Tantalum base alloys



United States Patent 3,132,940 TANTALUM BASE ALLOY Alexander L. Field, 512, Pittsburgh, and Robert L.

Ammon, Pleasant Hills, Pa, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania No Drawing. Filed .lan. 17, 1962, Ser. No. 166,954 3 (Zlaims. (Ci. 75-174) The present invention relates to tantalum base alloys suitable for use where high strength and ductility at elevated temperatures are required.

Fabricable alloys possessing strength and ductility at extremely high temperatures have many industrial and military applications, and it is generally recognized that future developments in many fields are closely tied to the availability of new and improved alloys possessing these properties. For example, the development of Space propulsion units, re-entry vehicle structures, improved rocket nozzles, blades for gas turbines and radiation heat exchangers are dependent upon the availability of such alloys.

In accordance with this invention, it has been found that workable alloys possessing unusually high strength and ductility at temperatures above 2000" F. can be produced by alloying tantalum with rhenium and molybdenum in specified proportions.

The object of the invention is to provide a readily workable cast member being characterized by relatively high strength at elevated temperatures and by relatively good ductility at room temperature, the member comprising predetermined proportions of rhenium and molybdenum and the balance, over 50% by weight being tantalum, with small amounts of incidental impurities.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

In accordance with the present invention wrought members have been produced from a cast member comprising a ternary tantalum base alloy comprising from 1% to 5% by weight rhenium, from 2% to by weight molybdenum, and the balance being tantalum, with small amounts of incidental impurities. In a preferred embodiment, the alloys of this invention comprise from 2% to 4% by weight rhenium, from 4% to 8% by weight mo lybdenum and the balance being tantalum with small amotmts of incidental impurities. The alloys are characterized by high mechanical strength and ductility at elevated temperatures, and the ability to be easily wrought to shape by hot or warm working, or in certain alloy compositions, by cold working. Incidental impurities and small amounts of additives may include zirconium, tungsten, cobalt, nickel and iron in amounts less than 1% The alloy may be melted by one or" several procedures which will insure homogeneity and a minimum of contamination. For example, unalloyed, high purity, tantalum together with the proper amounts of pure rhenium and molybdenum can be fed into a conventional nonconsumable arc melting furnace containing an inert atmosphere, such as argon or vacuum. The resulting ingot may be remelted several times, preferably by nonconsumably arc melting it, to achievehomogeneity, then may be hot worked to the desired shape. The alloy may also be prepared by pressing together powders of tantalum, rhenium, and molybdenum and consumably arc melting the same. The alloy may also be prepared by levitation melting of a ball or rod of the alloy, using induction heating. Electron beam melting of the alloys is also satisfactory.

The following example is illustrative of the, present invention.

An alloy comprising'92% tantalum, 4% molybdenum, and 4% rhenium was prepared by blending powders of tantalum, molybdenum, and rhenium, compacting the powders to rectangular bars at 25 to 50 tons per square inch pressure and sintering the bars at 3000 F. in a vacuum for 2 hours. The alloy bar Was consumably arc melted in a vacuum of less than 1 micron using a 60 cycle single phase A.C. power at 2800 amperes and 20 volts for a inch by inch electrode cross section, the melt rate being from 1.4 to 1.8 pounds per minute. The resultant bar was extruded at a temperature of 3100" F. at a pressure of 1800 p.s.i. The resulting bar was then rolled at 2250 F. with 50 mils reduction per pass. Finally, the resulting sheet or strip was stress relieved for one hour at 2015 F. Samples were cut from the sheet and were tested at temperatures of 2200 F. and 2500 F. for ultimate tensile strength, yield strength, percent elongation and percent reduction in area. The following results were obtained:

70, 300 42, 800 81, 600 49, 200 Reduction of Area. crcent" 8. 4 17.6 Total Elongation do 6. 4 13. 5

It may be concluded from these tests that the alloy has a relatively high strength and ductility at elevated tem peratures.

Other alloys containing from 1 to 5% rhenium, from 2 to 10% molybdenum, balance tantalum may be prepared with good properties.

It will be understood that the above description is illustrative and not limiting.

We claim as our invention:

1. A readily workable member comprising a tantalum base alloy consisting essentially of by weight from 1% to 5% rhenium, from 2% to 10% molybdenum and the balance tantalum with small amounts of incidental impurities, the cast member being characterized by relatively high strength and good ductility at elevated temperatures.

2. A readily workable member comprising a tantalum base alloy consisting essentially of by weight from 2% to 4% rhenium, from 4% to 8% molybdenum and the balance tantalum with small amounts of incidental impurities, the cast member being characterized by relatively high strength and good ductility at elevated temperatures.

3. A readily workable member comprising a tantalum base alloy consisting essentially of by weight 4% rhenium, 4% molybdenumand the balance tantalum with small amounts of incidental impurities, the cast member being characterized by relatively high strength and good ductility at elevated temperatures.

Steel, May 8, 1961, page 126, relied upon. Journal of Metals, July 1961, pages 487-489 relied upon, article by Schmidt et a1. 

1. A READILY WORKABLE MEMBER COMPRISING A TANTALUM BASE ALLOY CONSISTING ESSENTIALLY OF BE WEIGHT FROM 1% TO 5% RHENIUM, FROM 2% TO 10% MOLYBDENUM AND THE BALANCE TANTALUM WITH SMALL AMOUNT OF INCIDENTAL IMKPURITIES, THE CAST MEMBER BEING CHARACTERIZED BY RELATIVELY HIGH STRENGTH AND GOOD DUCTILITY AT ELEVATED TEMPERATURES. 